ABSTRACT

Ataxia refers to impaired ability to coordinate muscle activity in the execution of voluntary movement. Clinically, important findings include broad based gait, errors in range and force of limb movement (dysmetria), errors in rate and regularity of repetitive and alternating movements (dysdiadochokinesia), and tremor that is usually most marked at the end of movement. Anatomically, this involves most prominently pathology of the cerebellum and=or its afferent or efferent connections. A clinician’s efforts primarily involve diagnosis and supportive care, as few useful specific medical therapies are available. Challenges to proper diagnosis of genetic causes include: (1) variable phenotypes and ages of onset within individual genotypes, and (2) overlapping phenotypes among different genotypes.